The present invention relates to a control method and a control system, and more specifically, to a control method and a control system appropriate for a copier, or similar apparatus.
Recent enhancement in the functions of office automation apparatuses (OA apparatuses) has been conspicuous due to the progress of computer technology. However, in proportion to the enhanced functions, the control of these apparatuses has become more complicated and highly advanced, and thereby, an increase in speed and capacity of CPUs for controlling OA apparatuses, an increase in scale of software, and a subsequent increase in the number and complexity of signal lines in the apparatuses, have become unavoidable. In FIG. 17, an example of a control of a copier by a conventional CPU is shown. In FIG. 17, it can be seen that the CPU1 provided on a control board, a plurality of various loads, and sensors are connected by parallel signal lines, and functional sections of the copier are all collectively controlled. There is a possibility that an increase of the number of signal lines and their complexity due to the centralization control results in a decrease of reliability due to induction noise from other signal lines, or imperfect contact of connectors.
Some conventional copiers operate according to a method in which controlled systems are separated into several operation blocks, and the control is distributed into these blocks by providing a CPU in each operation block. FIG. 18 is a block diagram of the distributed system of such a conventional copier. In this example, a main CPU 2, provided on one control board, and sub CPUs 3, respectively provided in each function section, are connected by exclusive-use serial communication lines 4, and each sub CPU 3 and each load, and each sensor are connected by parallel signal lines. Due to this structure, an increase in the number of signal lines and the complexity of the signal lines in the apparatus are suppressed to some degree. However, when the number of sub CPUs 3 is increased, the number of exclusive-use serial communication lines 4 is subsequently increased. Further, in a conventional serial communication function, internal interruption occurs during transmission and reception of signals, and a processing operation, currently being conducted, is interrupted once so that interrupt processing can be carried out at every occurrence of an interruption. Thereby, when the number of serial communication lines 4 is increased, the interrupted period of time of the main CPU 2 is increased, and therefore the influence on the processing which is currently being conducted, becomes not negligible.
Also known is a LAN (Local Area Network) system in which communication lines are commonly used by a plurality of CPUs. FIG. 19 is a block diagram showing an example of a distributed system of a copier used in conventional LAN systems. The same blocks as in FIG. 18 are shown by the same numerals. The main CPU 2 and each sub CPU 3 are connected by a common serial communication line 5. In this example, the communication line is commonly used by each block, and thereby, when the number of sub CPUs is increased, an increase in the number of communication lines is suppressed. However, when the number of sub CPUs 3 is increased, the degree of interference of the communication lines 5 is correspondingly increased. Accordingly, even when urgent communication is required, the number of chances, in which communication can not be carried out because another sub CPU 3 is using the communication line 5, is increased, and thereby, the influence on urgent processing becomes not negligible.
FIG. 20 is a view showing an example of a conventional LAN system (Japanese Patent Publication Open to Public Inspection No. 69947/1981). In FIG. 20, (a) is a block diagram showing the structure of a conventional LAN system, and (b) is the time chart of (a). In FIG. 20 (a), symbols A, B, C are operation blocks, DATA is a data bus, IRQ is a signal line for data transfer request, and DAR is a data ready signal line. In FIG. 20, initially, IRQ falls, after which, DAR rises, and then data is outputted. When data has been transferred, IRQ rises, after which, DAR falls, and one sequence is completed. In this example, there is no relationship between the main and sub CPUs in operation blocks A, B and C, they are in the same order, and there is no priority among the operation blocks. FIG. 20 is not structured by considering conditions of the response speed, required as in the control of a copier, such as an optical system control in which a relatively high speed response is required, a process control of a drum and its relating apparatus in which an intermediate speed response is allowable, or a transfer sheet conveyance system control in which a lower speed response is also allowable. As a result, the influence on the urgent processing in the high speed response system is not negligible. Further, in a plurality of operation blocks, IRQs can simultaneously fall, resulting in interference of data.
FIG. 21 is a view showing another example of a conventional LAN system (Japanese Patent Publication Open to Public Inspection No. 7651/1983). This example is composed of a main block 6 and a plurality of sub blocks 7. In this structure, the sub blocks 7 can not transmit data by themselves until they are called by the main block 6. Therefore, even when urgent communication is required by the sub blocks 7, the possibility in which communication can not be carried out, is increased, and adverse influence on the urgent processing is a distinct possibility.
A system shown in FIG. 22 (Japanese Patent Publication Open to Public Inspection No. 114306/1986) is also composed of a main CPU 8 and sub CPUs 9 as shown in FIG. 20, and the main CPU 8 and the sub CPUs 9 are connected with a communication line 10. Also in this system, the sub CPUs 9 can not transmit data by themselves until they are called by the main CPU 8. Therefore, even when urgent communication is required by the sub CPUs 9, the possibility in which communication can not be carried out, is increased, and the influence on the urgent processing becomes not negligible.
The LAN system shown in FIG. 23, is a case in which operation blocks 11 and 13 are connected with respective communication lines 14 and 15, in a closed loop, through a LAN interface section 12 (Japanese Patent Publication Open to Public Inspection No. 114306/1986). In each operation block, a main block and sub blocks are provided. However, this system is structured as a delivery system in which all operation blocks are connected in a loop, and therefore, when it is required to transmit data from one operation block to another operation block, a transmission delay is increased, caused by transmission through the non-relating transmission loop. Further, the operation block can not transmit data by itself before being called by another operation block. Therefore, even when urgent communication is required by each operation block, the possibility in which communication can not be carried out, is increased, and an influence on the urgent processing is not negligible.
The system shown in FIG. 24, is also a case in which operation blocks 16 are connected by a loop communication line 17 in the same manner as in FIG. 23 (Japanese Patent Publication Open to Public Inspection No. 281046/1987). In this case, there is a problem which is the same as in the system in FIG. 23. That is, when it is required to transmit data from one operation block to another operation block, a transmission delay, caused by transmission through the non-relating transmission loop, is increased. Further, the operation block can not transmit data by itself before being called by another operation block. Therefore, even when urgent communication is required by any operation block, the possibility in which communication can not be carried out, is increased, and an influence on the urgent processing is not negligible.
As described above, in the conventional systems, control is not conducted by taking into consideration conditions of the speed of each operation block, and as a result, there is a problem in that quick communication can not be performed, even when urgent communication is required by one of the operation blocks.